Influenza Activity in Switzerland : Actual Situation

Update January 23th, 2019

Influenza like illnesses weekly report

In the Northern and Southern hemispheres, influenza infections occur seasonally. So far, Influenza outbreaks are observed every winter in Switzerland. From one year to the next the influenza outbreak varies in  intensity, duration, circulating viral strains and the impact on the population. In order to inform the population and doctors of time of the wave of influenza and the coverage of influenza by the vaccine, the FOPH publishes from October to April a weekly report with a risk assessment.

Week 3/2019

The spread of influenza illness in Switzerland is currently widely spread. During week 3, 142 physicians from the Sentinella surveillance system reported 17.3 cases of influenza 1000 consultations. Extrapolated to the general population, this rate corresponds to an incidence of 140 consultations due to influenza illness per 100,000 population. The seasonal epidemic threshold of 68 cases of influenza illness per 100,000 population was exceeded in week 2/2019 (Figure 1).

The highest incidence was in the 0-4 old age group (Table 1). The spread of influenza is widespread  in the Regions 1 (GE, NE, VD, VS) and 4 (LU, NW, OW, SZ, UR, ZG), and  very widespread in the Regions 2 (BE, FR, JU), 3 (AG, BL, BS, SO), 5 (AI, AR, GL, SG, SH, TG,ZH) and 6 (GR, TI).

Figure 1: Number of weekly visits due to influenza illness, extrapolated per 100,000 population

Figure 2: Incidence of consultations per 100,000 population and spread by Sentinella region during week 3/2019

Figure 2: Incidence of consultations per 100,000 population and spread by Sentinella region during week 1/2019Region 1 (GE, NE, VD, VS), Region 2 (BE, FR, JU), Region 3 (AG, BL, BS, SO), Region 4 (LU, NW, OW, SZ, UR, ZG), Region 5 (AI, AR, GL, SG, SH, TG, ZH), Region 6 (GR, TI).Gray: no spread, blue: sporadic spread, purple: general spread, red: widespread spread.

 

Data from the National Reference Centre for Influenza  (NRCI)

 

Influenza viruses detected per week. Cases are classified according to the sampling date. Proportions of medical consultations for influenza-like illness (ILI) out of 1000 consultations are also reported. FluA/B undet.: influenza A virus that is currently being subtyped, respectively. A H3N2 seasonal: influenza A (H3N2) virus. A H1N1 2009: influenza A (H1N1) pandemique 2009. ‰ ILI : percentage of influenza-like illness medical consultations per week reported to the Swiss Federal Office of Public Health by the Sentinel doctors.

During week 3, the National Influenza Reference Center (NCRI) detected Influenza A  viruses in 25 of the 53 samples analyzed as part of the Sentinella surveillance system. Since the beginning of the influenza season, the CNRI has demonstrated by inhibition of haemagglutination the following viruses in Sentinella samples:

Influenza A(H1N1)pdm09

- A/St Petersburg/27/2011-like

- A/California/7/2009-like

- A/Michigan/45/2015-like

Influenza A(H3N2)

- A/Singapore/INFIMH-016-19/2016-like

- A/Switzerland/9715293/2013-like

- A/Hong Kong/4801/2014-like

 
International influenza activity
In Europe, low to moderate influenza activity has generally been observed, with an increasing trend [1]. North America and Asia recorded high activity, with Canada and the United States both already exceeding their seasonal threshold [2-5]. In Canada, the peak of the vage has already passed [3]. The majority of viruses detected in Asia, Europe and North America belonged to the Influenza A (H1N1) subtype pdm09 followed by Influenza A (H3N2).
 

Links and references

1. European Centre for Disease Prevention and Control (ECDC). Seasonal Influenza - Latest surveillance data http://flunewseurope.org/   (accessed on 08.01.2019).

2. Weekly U.S. Influenza Surveillance Report http://www.cdc.gov/flu/weekly/index.htm   (accessed on 08.01.2019).

3. Canada Rapports hebdomadaires d’influenza. http://www.canadiensensante.gc.ca/diseases-conditions-maladiesaffections/disease-maladie/flu-grippe/surveillance/fluwatch-reports-rapports-surveillance-influenza-fra.php  (accessed on 20.11.2018).

4. China National Influenza Center weekly reports. http://www.chinaivdc.cn/cnic/   (accessed on 08.01.2019).

5. World Health Organisation (WHO) Influenza update – 332 http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance/en/   (accessed on 08.01.2019).

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Last update : 29/01/2019